Pneumatic cushion



June 14, 1966 y R. H. BLECKER ETAL 3,255,469

PNEUMATIC CUSHION Filed Feb. 25. 1964 I ISIN IN IN ISIN IDE IN IN IR.

INVENTORS RAYMOND H. BLECKER ROBERT C. COSTELLO MUNZER MAKANSI BY wwwATTORNEY United States Patent O 3,255,469 PNEUMAIIC CUSHION Raymond H.Bleeker, Homewood, and Robert C: Costello, Flossmoor, Ill., and MunzerMakansi, Wilmlngton, Del.; said Makansi assgnor to E. I. du Pont deNemours and Company, Wilmington, Del., a corporation of Delaware FiledFeb; 25, 1964, Ser. No. 347,298 4 Ciaims. (Cl. 5-351) T-his linventionrelates to the structure of upholstered articles, such as seat cushions,mattresses, box springs and the like, and more particularly to such.articles comprised of a particular spring insulator pad.

In the fabrication of lupholstered articles .it is irequently desirableto employ a spring insulator pad. Such a pad is interposed ybetween anunderlying spring structure and an overlying layer of relatively softpadding material for purposes of protecting the padding material fromdamage by the spring structure through abrading, scuffing or cutting, aswell as for -supporting the padding 1n the interspaces between elementsci the spring structure.

`Conventional types lof spring insulator pads include elted sisalsheets, burlap or similar woven fabrics, and films of various ilexibleplastic materials. The latter generally require tensile reinforcementfrom suitably elastic laments which are adhered to their surface. -Evenapart lfrom the increased manufacturing costs which are encountered inthe provision `ot-such reinforcement, the resultant pads also tend tocurl up so as to make it diicult to fasten yto the spring units. Thecustomarily used sisal pads display the variable properties associatedwith natural tiber products and `are subject to the variable costpatterns associated with imported materials. These observations pertainalso to the woven burlap sheets, which have the `further Vdeiiciency of'contributing little to the resiliency of the overall structure.

This invention provides upholstered articles having a spring insulator.pad material of constant predetermined physical properties, which isnot subject to the difficulties sometimes experienced With natural fibrematerials, and which contributes significantly to the overall resiliencyof the article. The pads employed in accordance with the invention alsohave the advantage of 'being readily stored and handled and be-ingeasily secured to the underlying spring structure. Further advantageso'f the articles of this invention will be .apparent from the remainderof the :specification and claims.

The improved spring insulator pad as employed in accordance with thisinvention comprises Ia pneumatic integral foam sheet of a syntheticpolymeric material comprised of predominantly closed cells, the sheetextending over substantially the entire upper surface o'f the springstructure of the upholstered article, and the sheet having a multitude'of lsmall spacedaapa-rt perforations extending from tone surfacethereof through the thickness of the sheet to the opp-osite surfacethereof.

A typical embodiment of the invention 'will nofw be described withreference to the drawings wherein:

FIGURE l is a tragmentary perspective view, partially broken away,showing a mattress, and

FIGURE 2 is an enlarged fragmentary sectional View taken along lineII-II of FIGURE l.

ice

yFIGURE 3 is la 'fragmentary perspective view, partially broken away, ofa spring insulator pad of crosslapped structure.

The upholstered article, in this case a mattress 10, includes anunderlying spring structure comprising a series of generally parallelupstanding coil springs 16, spring insulator pads I14 covering `bothsides of the spring structure, .and padding material 13, all enclosed bya lfabric 12 or other covering. A myriad of spaced apart perforations1'5 are provided in the sheet 14.

In lFIGURES a spring insulator pad structure C17 is shown comprising twocrosslapped foam sheets 18 and 20. ,These may be laminated together lbyan adhesive, not shown. Perforations 115 extend fully through thethickness of the pad 17. Arrows at the edges of the sheets show thedirection of sheet tor-mation and orientation.

It will tbe apparent that the nature of the spring structure is notmaterial to the invention so long as it is resiliently distortable underforce of a general magnitude imposed by the weight of a person restingthereon. Thus zig-Zag wire spring elements or other types of springs canalso be used. Similarly the overlying surface padding material maycomprise any of a number of materials, for example cotton wadding,iiberlill batting, urethane or foam rubber pads, or other materialscustomarily used in the art.

The cellular sheets employed as spring insulator pads in accordance withthe .present invention require certain essential :characteristics andproperties.` A number of commercially available foam materials 1as wellas others less well known nevertheless possess such features and hencecan 'be satisfactorily' utilized. A particularly essentialcharacteristic of a suitable foam is that it have a major proportion, bynumber, of closed cells since open cells do not ordinarily affordadequate properties with respect to pneumaticity. By pneumaticity inthis sense is meant that air or `other gas -is effectively continedwithin the cel-ls so that in conjunction 'with the resiliency providedby the cell walls, it can substantially contribute to the load bearingability of the pad. For practical purposes mere visual lor microscopicexamination will often readily reveal whether or not a particularcellular structure predom-inates in closed or open cells. Theclosed-cell content of a yieldable foam sample may be determined by thegas displacement Vmethod of Remington and Pariser, Rubber World, May1958, p. 26d, modiiied yby operating at as `low a pres-sure differentialas possible to minimize volume changes of the yieldalble closed cells.

A further essential characteristic of the `tfoams to be employed in thestructures of this invention is that they lbe yieldable, i.e. resilientsuch that substantial deformation occurs upon application of mechanicalpressure. By substantial deformation is meant that the cellularstructure is yieldable such that its volume can be compressed by Iatleast about 10% under a load ot 10 lbs. per square inch sustained for aperiod of l second with recovery of at least about 50% of its originalvolume on release of lthe load. Foams which do not compress to thatextent are generally too rigid and hence do not afford a suilcientdegree of resiliency.

The wall portions of the cellular sheets are composed of a synthetic,high molecular weight thermoplastic polymer. The polymers may beselected from a wide variety of organic addition and condensationpolymers, provided, of course, that in the form of a ycellular structurethey possess the described essential characteristics. Typical of suchpolymers are the polyolens such as polyethylenes, linear or branched,polypropylene, polyamides such as nylon 6 or polyesters such aspolyethylene terephthalate, halohydrocarbon polymers such aspolychlorotriuoroethylene, etc. The manufacture of cellular materials insheet form from such polymers is well known in the art as illustrated byU.S. Patents 2,948,665, 2,945,261 and 2,256,483. A preferred class ofcellular structures is that prepared from crystalline organic syntheticpolymers, since excellent strength and pneumaticity properties areafforded therewith.

Cellular sheets of the above description tend to possess a high tensilestrength and toughness. These properties are important for springinsulator pad duty; that is, the pad must withstand repeated flexing inthe thickness direction as well as considerable stresses in thetransverse directions. By virtue of the predominance of individualclosed cells, the cellular sheet itself has a pneumatic character andcontributes significantly to the overall resiliency of the structure.Low density cellular sheets having thin Walled cells provide for ecientuse of the polymer while maximizing the strength of the sheet.

The total thickness of the cellular sheet may range from about ls" to 2"or even thicker. The higher thicknesses are preferred where theapertures of the associated spring unit are large, i.e. increasedthickness giving rise to greater stiffness and improved ability tobridge across the larger apertures and prevent capping of the surfacepadding. The integral insulator pad may be either a single foam sheet ora laminate of individual pneumatic foam sheets in variousconfigurations, such as crosslaminated sheets. The foam insulator padsmay, of course, be laminated to lm, paper, fabric, and other surfacinglayers, where desired.

As an essential feature of the invention, the foam spring insulator padsmust be perforated in order to minimize the drumming problem which tendsto occur when a flat sheet of appreciable area extends across thesurface of a spring unit. These perforations apparently either break upthe undesirable vibration patterns otherwise set up in the unperforatedsheets, or permit a freerfiow of air through the sheet, or in some othermanner minimize the drumming sound generated when the assembledcushioning unit is rapidly loaded or unloaded. The shape, size anddistribution of the perforations appear to be relatively uncritical.Nevertheless the perforations should be -small compared with thedimensions of the individual elements in the underlying spring unit,i.e. so that portions of the spring structure do not become lodgedWithin the pad holes. The perforations can have a Variety ofcross-sections, e.g. be round, rectangular, oval, or triangular,although the area of each cross-section should preferably range upwardsfrom 0.0004 square inch. In a preferred embodiment, the holes have across sectional area of 0.005 to .500 square inch. The perforations maybe prepared by punching, cutting, slitting and laterally stretching,melting or any other technique known in the art. One suitable patternconsists of approximately 1A" diameter holes perforated in a squarepattern on 11/2 centers.

Polypropylene is the preferred polymer from which these foam springinsulator pads are prepared, although foam sheets with the requiredphysical properties may also be prepared from various other syntheticpolymers. The preference for polypropylene in the present inventionresides in a favorable combination of low cost of polymer, excellenttensile properties of the product, adequate retention of pneumaticity,and generally pleasing aesthetics.

The spring insulator pads of this invention may readily be incorporatedin upholstered articles in any of a number of ways. For example, a padwhich is co-extensive with the surface of the spring unit may befastened thereto at intervals along the edge of the spring unit byconventional techniques using hog rings, staples, tie straps, or bystitching. If the pad is somewhat larger in area than the surface of thespring unit, the resilience and vcompliance of these foam pads permitthe over-hang to be folded over and fastened along the sides of thespring unit. Such construction provides additional protection for theupholstery and padding from the edges of the spring unit. Again, due tothe desirable tendency of these foam pads to lie flat during assembly,it is possible simply to place the insulator pad on the surface of thespring unit with no special fastening at all, and depend on thesubsequently applied over-lying surface padding and fabric cover tomaintain the insulator pad in place. Furthermore, since they may beperforated without danger of runs or slits developing, these foaminsulator pads may also be employed in so-called tufted constructionswhere the assembly is fastened together by buttons on opposite surfacesof the upholsteredarticle tied together with cords passing through thebody of the unit (and hence also through the insulator pad).

The following specific example further illustrates the presentinvention.

Example A highly pneumatic closed cell polypropylene foam sheet isprepared at a thickness of approximately 0.030- 0.050" with a sheetdensity of approximately 1.25 lbs./ft.3. The sheet is cut into lengthsof 7.5 and 5.5 respectively. Eight layers of these cut lengths are thenlaminated together, in crosslapped orientation, using a rubber-basedadhesive diluted with chloroform to 2 weight percent solids. Theresulting structure is an eight-layer laminated sheet approximtaely 7.5long x 5.5 wide x 0.33 thick, weighing 580 g. and possessing balancedproperties in length and width dimensions. The resulting pad iscompressed to W16" thickness and simultaneously embossed with an S-meshwire screen pattern by placing it in a flat press at 70 C. and 70p.s.i.g. for five minutes between two S-mesh wire screens using 3/16thick shims (spacers) at the end of the two sides of the platens tocontrol thickness at 3/16. The embossed pad is then perforated withapproximately ls to 3716 diameter tapered holes melted in the sheet in a-square pattern on 1" centers. The pad is then trimmed to produce amattress spring insulator pad long x 57 wide x 0.19 thick at a densityof 2.0 lbs./ft.3.

Spring insulator pads prepared in the above manner are next aixed toopposite sides of a coil spring construction unit. The mattressfabrication procedure is then completed by conventional methods Wellknown in the art.

Even apart from other advantages, the weight saving of up to l0 lbs. permattress resulting from the use of the low density spring insulator padsis considered to have a great advantage not only in freight costs, butalso in handling the mattress in the plant during manufacturing and alsoat home where the mattress is used.

What is claimed is:

1. In an upholstered article having an underlying spring structure whichis resiliently distortable .under force of a general magnitude imposedby the weight of a person resting thereon, an overlying layer of paddingmaterial, and an interposed pad supporting said padding material andprotecting same from damage by said spring structure; the improvementwherein said interposed pad comprises a pneumatic integral foam sheet ofa synthetic polymeric material comprised of predominately closed cells,said sheet extending over substantially the entire upper surface of thespring structure, and said sheet having a multitude of small spacedapart perforatons extend- References Cited by the Examiner ing -from onesurface thereof through the thickness of Y UNITED STATES PATENTS thesheet to the opposite surface thereof.

3,080,579 3/1963 Gordon 5--354 cross sectional area of 0.005 to 0.500square inch.

4. The article of claim 1 wherein said foam sheet comprises acrosslapped structure of at least two individual 10 FRANK B' SHERRYPrimary Exammer' layers. C. A. NUNBERG, Assistant Examiner.

1. IN AN UPHOLSTERED ARTICLE HAVING AN UNDERLYING SPRING STRUCTURE WHICHIS RESILIENTLY DISTORTABLE UNDER FORCE OF A GENERAL MAGNITUDE IMPOSED BYTHE WEIGHT OF A PERSON RESTING THEREON, AN OVELYING LAYER OF PADDINGMATERIAL, AND AN INTERPOSED PAD SUPPORTING SAID PADDING MATERIAL ANDPROTECTING SAME FROM DAMAGE BY SAID SPRING STRUCTURE; THE IMPROVEMENTWHEREIN SAID INTERPOSED PAD COMPRISES A PNEUMATIC INTEGRAL FOAM SHEET OFA SYNTHETIC POLYMERIC MATERIAL COMPRISED OF PREDOMINATELY CLOSED